Referring to FIG. 12, a conventional selective one-way wrench 80 includes a head 81, a gear 86, a pawl assembly 87 and a switch 90. The head 81 defines a circular space 82, a crescent space 83 communicated with the circular space 82 and a circular cavity 84 communicated with the crescent space 83 and defined in an upper face thereof. The pawl assembly 87 includes two pawls 87 connected with each other by means of a spring 88. Each of the pawls 87 includes a rod 89 extending from an upper face thereof. The pawl assembly 87 is movably put in the crescent space 83. The rods 89 extend from the crescent space 83 into the circular cavity 84. The gear 86 is rotationally put in the circular space 82 for engagement with selective one of the pawls 87 at a time. The switch 90 includes a recess 91 defined in a lower face thereof. The recess 91 includes two ends. The switch 90 is rotationally put in the circular cavity 84 between two positions. Selective one of the rods 89 is put in one of the ends of the recess 91. Thus, the head 81 can drive the gear 86 in selective one of two directions by means of the pawl assembly 87. To retain the switch 91 in selective one of the positions, a spring-biased detent 96 is provided between the bottom of the circular cavity 84 and the lower face of the switch 90. The selective one-way wrench 80 is however weak for including the crescent apace 83 and the circular cavity 84. The selective one-way wrench 80 is complicated because the pawl assembly 87 includes two pawls 88 and a spring 89. The use of the spring-biased detent 96 adds to the complicacy of the elective one-way wrench 80. Moreover, it is difficult to install the pawl assembly 87 and the spring-biased detent 96.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.